The type of forming machine which this invention relates to includes upper and lower bases and a rear connecting portion extending between the upper and lower bases to cooperate therewith in defining a work space. Upper and lower slides are respectively mounted on the upper and lower bases for rectilinear movement and are adapted to carry a pair of forming racks that form a workpiece during the slide movement so as to provide a round outer surface of the workpiece with teeth or splines.
U.S. Pat. No. 2,995,964 discloses a forming machine of the type involved with the invention wherein the slides on which the forming racks are mounted are moved by a pair of hydraulic cylinders to provide the forming. Adjustment of the forming racks on the slides to control the extent of workpiece forming is provided by wedge adjusters interposed between the forming racks and their associated slides. A pair of driving rack members are fixed to the slides in a spaced and substantial parallel relationship to each other and are meshed with a drive gear mounted for rotation with a spindle support utilized to mount the workpiece. Tie bars extend between the upper and lower bases to prevent deflection therebetween during the workpiece forming. In commercial units actually sold of this type of machine, the tie bars have merely been comprised of metallic straps having opposite ends that are respectively bolted to the upper and lower bases.
One problem with the type of machine disclosed by U.S. Pat. No. 2,995,964 discussed above is that the hydraulic cylinders are only capable of providing precise forming during their retraction strokes since there is a tendency of the cylinders to buckle during extension. As such, forming can only be performed during one direction of movement, i.e. during the retraction stroke. Another problem involved with this type of machine is that the metal straps utilized for the tie bars permit a certain amount of deflection due to the manner in which the straps are merely bolted to the bases.
U.S. Pat. No. 3,793,866, which is assigned to the assignee of the present invention, discloses a forming machine of the type to which this invention relates wherein a pair of rotary hydraulic motors are utilized to drive the slides on which the forming racks are mounted. Each rotary motor drives a shaft having a drive gear that is meshed with a drive rack mounted on the associated slide. The shafts also have associated synchronizing gears that are meshed with a common synchronizing gear in order to coordinate the movement of the pair of slides and hence the movement of the pair of forming racks. Adjustable deflection control connections extend between the upper and lower bases to control the deflection therebetween as the forming is performed on the workpiece by the forming racks upon slide movement under the impetus of the pair of rotary hydraulic motors.
While the machine disclosed by U.S. Pat. No. 3,793,866 discussed above illustrates spur gears for meshing and driving the drive racks mounted on the slides, commercial machies of this type have included a pair of helical gears of opposite angular orientation on each drive shaft and a pair of drive racks having angular teeth of opposite orientations on each slide. Such a dual gear and drive rack construction is required with each slide in order to carry both the driving forces and the synchronization forces without overloading the ends of the teeth and possibly causing one or more teeth to break off. Also, the synchronizing gears are located between the rotary hydraulic motors and the drive gears and are accommodated within support housings which must be sufficiently strong to withstand the torque applied by the rotary hydraulic motors that are mounted on the housings. Furthermore, eccentric supports must be provided to remove backlash from between the common synchronizing gear and the synchronizing gears on the shafts.
U.S. Pat. No. 4,155,236, which is also assigned to the assignee of the present invention, discloses a forming machine of the type to which the invention relates wherein equal displacement hydraulic cylinders are utilized to reciprocate forming racks in order to permit driving thereof by a closed loop hydraulic system. Deflection control connections that extend between upper and lower bases of the machine include sleeves having opposite ends engaged with the bases and also include bolts that extend between the bases through the sleeves in order to preload the sleeves in an adjustable manner to thereby control deflection between the bases as the forming is performed.